This application and its disclosure generally relate to the field of precise and continuous (during a life time of an X-ray system) measurement of the Practical Peak Voltage (PPV) in a radiological practice.
Peak kilovoltage (kVp) is the maximum voltage applied across an X-ray tube. It determines the kinetic energy of the electrons accelerated in the X-ray tube and the peak energy of the X-ray emission spectrum. The actual voltage across the tube may fluctuate from an exposure to an exposure with the same, time, KvP and mA setting. Further, the age of a particular machine has a significant effect on mean kVp accuracy. Determination of the peak kilovoltage (kVp) applied to a particular X-ray tube plays a fundamental role in the evaluation of the system calibration and performance, and patient’ cumulative exposure dose quantification. Accordingly, it is very important to accurately determine the peak kilovoltage (kVp) accuracy of an individual X-ray unit during performance at each time the unit is used and to compare and monitor its values.
It is well-known in the industry, that small variations in kVp values may produce significant increases in patient absorbed doses due to the approximately squared dependence between the air kinetic energy released per unit of mass (air kerma) and kVp. The relation between the variation in the tube voltage and the variation of the absorbed dose depends upon the part of the body being irradiated and the used kVp range. Martin et al., for example, have evaluated anteroposterior radiographic views of the abdomen and reported a mean variation of the equivalent dose absorbed by the liver of 3.5% by kVp unit in the range between 60 and 120 kVp, 1%/kVp between 90 and 100 kVp and 13%/kVp between 60 and 70 kVp. Another study, described in Fung et al., has demonstrated that a variation in the voltage applied to the tube also produces a significant contribution to the patient absorbed dose due to the scattered beam.
The practical peak voltage (PPV) has been adopted as the reference measuring quantity for the x-ray tube voltage. However, the majority of commercial kV-meter models measure the average peak voltage, U(P); the average voltage, U; the effective voltage, U(eff); or the maximum peak tube voltage, U(P).
Most of the conventional measuring equipment are not capable of accurately measuring X-ray radiation due to the relatively low energy emitted. Traditionally, cumbersome ionization chambers are used for measuring X-ray radiation. They are big and require lots of equipment. X-ray energy contrast is significantly lower during exposures through the use of ionization chambers resulting in a very low contrast quality of an X-ray image. Radiologists either repeat the procedure trying to increase the quality of an image by increasing the kVp. That increases the radiation exposure. The inventors of the present application evaluated a utilization of a dose monitoring equipment and found that all studied, small and large facilities in NY and NJ, are currently not utilizing any means of registration of X-ray energy during an X-ray imaging procedure. They have also evaluated ten X-ray facilities in NY and exposed 10 X-ray emissions at specific setting for every spinal part. Total 40 X-rays were exposed at each X-ray machine corresponding 10 for cervical, 10 for thoracic, 10 for lumbar and 10 for lumbar-sacral anatomies. The result of the findings was as follows: 1) all of them produced different outputs readings with the same KvP and mA and time settings; 2) Not only they were producing different results on the same settings, but also the results within the settings produced different readings. These differences led to a conclusion that X-ray exposures are producing uncontrolled and unpredictable energies during every X-ray image procedure. This led the inventors to conclude that these energy outputs variations create health hazard conditions for the patients of the radiology facilities currently receiving uncontrolled, dangerously high and, most importantly, unknown and un-monitored levels of radiation exposures.